Clinical evidence for topotecan-paclitaxel non--cross-resistance in ovarian cancer

A large, randomized study comparing the efficacy and safety of topotecan versus paclitaxel in patients with relapsed epithelial ovarian cancer showed that these two compounds have similar activity. In this study, a number of patients crossed over to the alternative drug as third-line therapy, ie, from paclitaxel to topotecan and vice versa. We therefore were able to assess the degree of non-cross-resistance between these two compounds.

Patients who had progressed after one platinum-based regimen were randomized to either topotecan (1.5 mg/m(2)/d) x 5 every 21 days (n = 112) or paclitaxel (175 mg/m(2) over 3 hours) every 21 days (n = 114). A total of 110 patients received cross-over therapy with the alternative drug (61 topotecan, 49 paclitaxel) as third-line therapy.

Response rates to third-line cross-over therapy were 13.1% (8 of 61 topotecan) and 10.2% (5 of 49 paclitaxel; P =.638). Seven patients who responded to third-line topotecan and four patients who responded to paclitaxel had failed to respond to their second-line treatment. Median time to progression (from the start of third-line therapy) was 9 weeks in both groups, and median survival was 40 and 48 weeks for patients who were receiving topotecan or paclitaxel, respectively. The principal toxicity was myelosuppression; grade 4 neutropenia was more frequent with topotecan (81.4% of patients) than with paclitaxel (22.9% of patients).

Topotecan and paclitaxel have similar activity as second-line therapies with regard to response rates and progression-free and overall survival. We demonstrated that the two drugs have a degree of non-cross-resistance. Thus, there is a good rationale for incorporating these drugs into future first-line regimens.